A power supply system of a hybrid vehicle is known that steps up a low output voltage from a battery by a voltage step-up converter and supplies electric power of the high stepped-up voltage to a motor generator. Regarding such a power supply system, a technique of reducing an electric power loss of the voltage step-up converter has been proposed.
For example, a hybrid vehicle disclosed in Japanese Patent Laying-Open No. 2010-11651 (PTL 1) includes first and second batteries, a first voltage step-up converter converting an output voltage of the first battery to output the converted voltage to a motor generator, and a second voltage step-up converter converting an output voltage of the second battery to output the converted voltage to the motor generator. While controlling the vehicle in a hybrid travel mode, a control device of this hybrid vehicle operates the first voltage step-up converter while stopping the second voltage step-up converter. In this way, an electric power loss of the second voltage step-up converter is reduced and accordingly fuel economy can be improved.